Angle - Units Of Measurement Of An Angle, Geometric Characteristics Of Angles

single ancient ray vertex

An angle is a geometric figure created by two line segments that extend from a single point or two planes which extend from a single line. The size of an angle, measured in units of degrees or radians, is related to the amount of rotation required to superimpose one of its sides on the other. First used by ancient civilizations, angles continue to be an important tool to science and industry today.

The study of angles has been known since the time of the ancient Babylonians (4,000-300 B.C.). These people used angles for measurement in many areas such as construction, commerce, and astronomy. The ancient Greeks developed the idea of an angle further and were even able to use them to calculate the circumference of Earth and the distance to the moon.

A geometric angle is formed by two lines (rays) that intersect at a common endpoint called the vertex. The two rays are known as the sides of the angle. An angle can be specified in various ways. If the vertex of an angle is at point P, then the angle could be denoted by LP. It can be further described by using a point from each ray. For example, the angle LOPQ would have the point O on one ray, a vertex at point P, and the point Q on the remaining ray. An angle can also be denoted by a single number or character which is placed on it. The most common character used is the Greek letter θ (theta).

Additional Topics

An angle is commonly given an arithmetic value which describes its size. To specify its this value, an angle is drawn in a standard position on a coordinate system, with its vertex at the center and one side, called the initial side, along the x axis. The value of the angle then represents the amount of rotation needed to get from the initial side to the other side, called the terminal side. The d…

An angle is typically classified into four categories including acute, right, obtuse, and straight. An acute angle is one which has a degree measurement greater than 0° but less than 90°. A right angle has a 90° angle measurement. An obtuse angle has a measurement greater than 90° but less than 180°, and a straight angle, which looks like a straight line, has a 1…

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